1. Field of the Invention
The present invention relates to a coupling device, and more particularly to a coupling device for duct.
2. Description of the Prior Art
Typical ducts for air conditioning apparatus comprise a parallelepiped body having two ends that are required to be coupled to the other ducts for forming an air passage for the air conditioning apparatus. Typically, a square frame is first formed by welding process and is then secured to the end portion of the duct by welding process. It may take a long time to assemble the ducts together in order to form the air passage. In addition, the frames are normally made of alloy materials having zinc applied onto the outer peripheral surface by electroplating process. However, when the zinc material is heated in the welding process, poisonous gas will be generated and will hurt the workers. Accordingly, the workers or the operators are required to set up an air drawing facility for drawing and for discharging the poisonous gas. This further complicates the assembling works to the ducts.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional coupling devices for ducts.